Method for inhibiting oxygen and moisture degradation of a device and the resulting device

Description of related application

This application is filed in the United States on August 18, 2005, entitled "Method for Inhibiting Oxygen and Moisture Degradation of a Device and the Resulting Device". It claims the interests of patent application No. 11 / 207,691, which is incorporated herein by reference.

The present invention relates to a method for suppressing the permeation of oxygen and water and the accompanying deterioration of the device, and the device obtained. Examples of such devices include light emitting devices (eg, organic light emitting diode (OLED) devices), photovoltaic devices, thin film sensors, evanescent waveguide sensors, food containers and medicine containers. ..

The transport of oxygen or moisture through the laminate or encapsulation material, and the concomitant attack of internal materials, such as light emitting devices (OLED devices), thin film sensors, and evanescent waveguide sensors. There are two more common degradation mechanisms involved in many devices. See the following references for a detailed discussion of issues related to the penetration of oxygen and moisture into the inner layers (cathodes and electroluminescence materials) of OLED devices and other devices.

Non-patent document 1 Non-patent document 2 Non-patent document 3 If nothing is done to minimize the penetration of oxygen or moisture into the OLED device, it will have a significant impact on lifespan. Much effort has been made to ensure that OLEDs have an operating life of 40,000 hours, but this level is required for OLED devices to outperform older display technologies, as described in the following literature: It is generally regarded as a thing.

Non-patent document 4<nplcit num="1"><text>Aziz, H., Popovic, ZD, Hu, NX, Hor, AH, and Xu, G. "Degradation Mechanism of Small Molecule-Based Organic Light-Emitting Devices," Science, 283, 1900-1902, (1999).</text></nplcit><nplcit num="2"><text>Burrows, PE, Bulovic., V., Forrest, SR, Sapochak, LS, McCarty, DM, Thompson, ME "Reliability and Degradation of Organic Light Emitting Devices", Applied Physics Letters, 65 (23), pp. 2922-2924</text></nplcit><nplcit num="3"><text>Chatham, H., "Review: Oxygen Diffusion Barrier Properties of Transparent Oxide Coatings on Polymeric Substrates", 78, pp. 1-9, (1996)</text></nplcit><nplcit num="4"><text>Forsythe, Eric, W., "Operation of Organic-Based Light-Emitting Devices, in Society for Information Display (SID)" 40th anniversary Seminar Lecture Notes, Volume 1, Seminar M5, Hynes Convention Center Boston, MA, Massachusetts, May 20 and 24 (2002)</text></nplcit>

<p> More prominent efforts to extend the life of OLED devices include gettering, encapsulation and extensive device sealing techniques. Currently, one common method for sealing OLED devices is to use different types of epoxy resins, inorganic and / or organic materials, which are UV curable or vary. A seal is formed after being heated by any means. For example, Vitex Systems manufactures and offers a coating under the trade name Barix for sale. This is a composite-based technique that uses alternating layers of inorganic and organic materials to seal the entire surface of the OLED device. While these types of seals provide some sealing performance, they can be very expensive and often cannot prevent oxygen and moisture from diffusing into the OLED device during long-term operation.</p><p> Similar oxygen and moisture permeation problems are also common in other types of devices such as thin film sensors, evanescent waveguide sensors, food containers and drug containers. Therefore, it is necessary to suppress the permeation of oxygen and moisture into devices such as OLED devices, thin film sensors, evanescent waveguide sensors, food containers and chemical containers. These and other needs are met by the present invention.</p>

<p> In the present invention, an LLT (low liquidus temperature) material, which usually has a low liquidus temperature (or low glass transition temperature in certain embodiments), is used to form a barrier layer on the device. As an LLT material, tin fluorophosphate (tin) fluorophosphate) glass, chalcogenide glass, tellurite glass, borate glass, but not limited to them. The LLT material is attached to the device by, for example, sputtering, simultaneous evaporation, laser ablation, flash evaporation, spraying, pouring, frit welding, vapor deposition, immersion coating, coating or roll coating, spin coating, or any combination thereof. be able to. Defects in the LLT material caused by the adhesion step can be removed by a consolidation step (eg, heat treatment) to form a protective coating on the device that is non-perforated and impervious to gas and moisture. Many bonding methods are possible for ordinary glass (ie, those with a high melting temperature), but the solidification step is actually useful for LLT materials with a sufficiently low solidification temperature so as not to damage the inner layer in the device. Only in the case of. In other embodiments, the adhesion and / or heat treatment steps are performed in vacuum, in an inert atmosphere, or in ambient conditions, depending on the composition of the LLT.</p><p> The present invention can be further fully understood if considered in conjunction with the accompanying drawings with reference to the following detailed description.</p>

FIGS. 1 and 2, respectively, show a flowchart of Method 100 for suppressing oxygen and moisture degradation of the device 200 and a side sectional view of the protected device 200. As described below, the device 200 includes a heat treated low liquidus temperature (LLT) material 202, one or more inner layers 204 and a support 206. Method 100 also includes step 102 of attaching the LLT material 202 onto one or more inner layers 204 placed on top of the support 206 (eg, substrate 206) (see also FIG. 5). LLT material 202 includes, for example, sputtering, flash evaporation, spraying, pouring, frit welding, vapor deposition, dip coating, coating, roll coating (eg, of LLT material 202 for membranes), spin coating, simultaneous deposition, laser ablation, Alternatively, they can be adhered using any of a variety of methods, including any combination thereof. Alternatively, the plurality of LLT materials 202 can be simultaneously adhered (eg, sputtered) onto one or more inner layers 204 placed on top of the support 206 (eg, substrate 206). In addition, multiple layers of the same or another type of LLT material 202 are adhered (eg, sputtered) onto one or more inner layers 204 placed on top of the support 206 (eg, substrate 206). )be able to. Method 100 also includes step 104 of annealing, solidifying or heat treating the device 200 containing the adhered LLT material 202. Heat treatment step 104 is performed to remove defects (eg, holes) in the LLT material 202 formed during adhesion step 102. Some examples of various devices 200 that can be protected by the heat treated LLT material 202 are light emitting devices (eg, OLED devices), photovoltaic devices, thin film sensors, evanescent waveguide sensors, food containers and chemical containers. Adhesion step 102 and heat treatment step 104 can be performed in vacuum or in an inert atmosphere. This is because the moisture is removed throughout the sealing process. This is to ensure that the oxygen-free state is maintained. This is especially important for robust organic electronics with a long working life with minimal degradation.

In one embodiment, the device 202 is an OLED device 200 having a plurality of inner layers 204 containing an electroluminescence material and a cathode placed on a substrate 206. The cathode and electroluminescence material 204 are easily damaged when heated to, for example, above 100-125 ° C. Therefore, if conventional glass is attached onto the OLED device 200, heat treatment step 104 (to minimize or eliminate porosity) would not be possible in this particular application. This is because the temperature required to remove defects in conventional glass (soda lime) is so high (eg 600 ° C) that the inner layer 204 of the OLED device can be damaged. However, in the present invention, the heat treatment step 104 can be performed in this particular application. This is because the temperature required to remove defects in the LLT material 202 (eg 120 ° C) can be relatively low, so the inner layer 204 of the OLED device will not be damaged. ..

When using the LLT material 202, all of this is possible because this type of material has a relatively low liquidus temperature (1000 ° C). The low liquidus temperature means that the LLT202 can be heat treated at a relatively low temperature that does not thermally damage the inner layer 204 of the OLED device in order to obtain a poreless film. Furthermore, the heat-treated LLT material 202 is susceptible to (eg) moisture, oxygen or other gases, such as thin film sensors, photovoltaic devices, evanescent waveguide sensors, food containers, chemical containers or electronic devices. It should be understood that in addition to the OLED device 202, it can also be used as a barrier layer on a wide variety of devices 200.

In a preferred embodiment, the LLT material 202 has a low liquidus temperature of 1000 ° C (more preferably 600 ° C, even more preferably 400 ° C), and the LLT material includes, for example, tin. Glasses such as fluorophosphate glass, chalcogenide glass, tellurite glass, borate glass and phosphate glass (eg, alkali Zn or SnZn pyrophosphate) can be mentioned. Such LLT material 202 is desirable for several reasons (for example), including:

Low liquidus temperature (LLT) materials can be free of heavy metals and other environmentally undesired materials.

-LLT material is durable even when immersed in water at 85 ° C and can have a low dissolution rate (less than 20 microns per day). See Tick, PA, "Water Durable Glasses with Ultra Low Melting Temperatures," Physics and Chemistry of Glasses, 25 (6) pp. 149-154 (1984).

-LLT material can contain dye molecules, 8 mM (4.8 x 10)¹⁸cm^-3) Can be included. See Tick, PA, Hall, DW, "Nonlinear Optical Effects in Organically Doped Low Melting Glasses", Diffusion and Defect Data, Vol. 53-54, pp. 179-188, (1987).

-LLT phosphate glass has a helium permeability coefficient that is 10,000 to 100,000 times smaller than that of quartz glass. See Peter, KH, Ho, D., Thomas, S., Friend, RH, Tessler, N. "All-Polymer Optoelectronic Devices", Science, 285, pp. 233-236, (199).

The tin fluorophosphate glass 202 will be described first. Table 1 shows the preferred composition range (parts by weight) of the various components.<tables num="1"><img file="JP5113054B2_D0001.tif" /></tables>

For a detailed description of tin fluorophosphate glass 202, refer to the following documents.

-US Pat. No. 4,314,031 -US Pat. No. 4,379,070 Tick, PA, Weidman, DL, "Optical Waveguides from Low Melting Temperature Glasses with Organic Dyes", in Proceedings of SPIE-The International Society for Optical Engineering-Nonlinear Optical Properties of Organic Materials V, pp. 391-401, (1993) ).

Tick, PA, "Water Durable Glasses with Ultra Low Melting Temperatures", Physics and Chemistry of Glasses, 25 (6) pp. 149-154 (1984) Tick, PA, Hall, DW, "Nonlinear Optical Effects in Organically Doped Low Melting Glasses", Diffusion and Defect Data, Vol. 53-54, pp. 179-188, (1987) The contents of the above documents are incorporated herein by reference.

Three different tin fluorophosphate glasses 202 (composition numbers 1-3), one tellurite glass 202 (composition number 4) and one borate glass 202 (composition number 5) were tested. Details of these LLT glasses 202 tested and the results and conclusions of their experiments are described below. Tables 2A and 2B show the composition of the exemplary LLT glass 202 tested, their T._G(In this and other examples herein, T_GIs related to low liquidus temperature) and shown with various components, as follows.<tables num="2A"><img file="JP5113054B2_D0002.tif" /></tables><tables num="2B"><img file="JP5113054B2_D0003.tif" /></tables> The LLT glass 202 tested is durable as shown in FIGS. 3 and 4. FIG. 3 is a graph showing the results of a weight loss experiment conducted in water at 85 ° C for 1000 hours. As can be seen, the LLT glass 202 (composition numbers 1, 2 and 4) tested is as durable as Corning Inc.'s 1737 glass (conventional glass). FIG. 4 is a graph showing weight loss measurements of the tested LLT glass 202 (composition numbers 1, 4 and 5).

A "calcium patch" experiment was also conducted. The experimental data obtained will be described below to show that the permeability of oxygen and water passing through one of the LLT glass film layers 202 (Composition No. 1) described above is low. Figure 5 shows LLT glass film 202 (composition number 1), two inner layers 204 (Al and Ca) and substrate 206 (Corning). It is a side sectional view of the oven 502 containing the device 200 equipped with the 1737 glass substrate of Inc.). Layers 204 of Al and Ca were adhered onto a thick substrate 206 and then sealed with LLT glass film 202 (composition number 1). During this experiment, some of the devices 200 were placed in oven 502 and exposed to environmental aging at constant temperature and humidity (typically 85 ° C and 85% relative humidity (85/85 test)). .. In each of the devices 200 tested, the Ca layer 204 was initially a highly reflective metal mirror. Then, when water and oxygen permeated the LLT glass film 202, which is the upper encapsulation layer, the metal Ca204 reacted and changed into an opaque white flake-like crust. This mass could be quantified by optical measurement (see Figures 6 and 7).

More specifically, the "calcium patch" test was performed as follows. A 100 nm Ca film 204 was evaporated onto Corning Inc.'s 1737 glass substrate 206. Then, the 200 nm Al layer 204 was attached onto the Ca film 204 by evaporation. Al layer 204 was used to simulate cathode conditions commonly used in the manufacture of polymer light emitting diodes (PLEDs). "Dual-boat" Using a custom Cressington evaporator, 1737 glass substrate 206 at 130 ° C and approximately 10 during the Ca and Al evaporation steps.^-6Maintained in tor. After cooling to room temperature, break the vacuum, then remove the calcium patch, place in a vacuum dryer and carry to the RF sputtering vacuum system, using a pump overnight 10^-6I put it back in the tor. LLT glass 202 (composition number 1) is then subjected to relatively mild RF power deposition conditions (30 W forward RF power / 1 W reflected RF power) and low argon pressure (approximately 19 sccm). Then, it was attached to the layer 204 of Al and Ca by sputtering (see step 102 in FIG. 1). Sputtering was carried out for 24 hours to obtain a glass thickness in the range of 2.5 μm (chamber pressure about 10).^-3Torr). It should be noted that the thickness of the LLT material can be the required thickness, depending on the duration of adhesion selected. After that, some of the newly prepared devices 200 were heated to about 121 ° C with an infrared lamp mounted in a vacuum chamber to solidify the sputtered LLT glass layer 202 (see step 104 in FIG. 1). See the top row of the photo in Figure 6). Upon cooling, the vacuum was broken and the heat-treated and non-heat-treated device 200 were placed in a humidity chamber and kept at 85 ° C and 85% relative humidity. During this time, photographs were taken at regular time intervals to quantify the gradual changes in the device 202 under test. Figure 6 shows an explanatory diagram of changes in the calcium membrane of the device 200 under test (created under somewhat different conditions).

FIG. 6 shows photographs of the device 200 under test taken at regular intervals to track the rate of calcium oxidation. The oxidation rate of calcium indicates the permeability of LLT glass film 202. The left panel of Figure 6 (labeled "general starting state") shows the oxidation reactions associated with this test (ie, Ca + 2H).₂O Ca (OH)₂+ H₂, And 2Ca + O₂ Shows the initial metal Ca layer 204 of the device 200 under test before 2CaO) occurs. The image in the bottom row is an image of a sample device 200 made without heating the glass layer 202 sputtered with LLT glass, taken at the time intervals shown. The captured image in the middle row is an image of a similar device 200 heated (121 ° C) for the first hour of the 24-hour glass attachment time interval. The device 200 to be tested, shown in the top row, was made in the same manner except that it was heated (121 ° C) after a 24-hour glass attachment time interval. The device 200 under test, shown in the top row, which was heat treated over the entire thickness of the LLT glass, clearly best prevented attacks by oxygen and moisture.

The photograph in FIG. 6 calculated and quantified the percentage of the region that changed to "white flake-like mass" with respect to the percentage of the region that maintained the "silver metallic luster finish", and plotted the calculated value as a function of time ( See Figure 7). Figure 7 shows the calcium oxidized for the time spent in oven 502 at 85 ° C and 85% relative humidity for three device under test 200 (see Figure 6) and one uncoated device. It is a graph which showed the percentage of a region. As shown, data 702 shows the percentage of oxidized calcium patch surface area on the calcium patch, with a 100 nm calcium layer and a 200 nm aluminum layer but not coated with LLT glass 202. Data 704 then shows the surface area of an oxidized calcium patch on one of the devices 200 under test with a 2.5 μm sputtered LLT glass layer 202 (composition number 1) (not heat treated). Data 706 shows the surface area of the oxidized calcium patch of another device under test 200 with a 2.5 μm sputtered LLT glass layer 202 (composition number 1), where the LLT glass layer is It was heat treated at 121 ° C for the first hour of the 24-hour adhesion period. Finally, data 708 shows the surface area of the oxidized calcium patch of another test device 200 with a sputtered LLT glass layer 202 (composition number 1) of 2.5 μm, in this case the LLT glass layer. Is heat-treated at 121 ° C for 1 hour after a 24-hour adhesion period. As can be seen, the performance of the device 200, which was heat treated after the adhesion period, was the best.

To generate this graph, we created a LabView code for each device 200 under test during the time spent in the 85/85 oven 502, the sequence shown in Figure 6. Processed the image. The "first image" on the left side of Figure 6 (before the device 200 under test was placed in the humidity oven) served as a reference criterion used to calculate the threshold. The threshold is the first minimum pixel intensity that occurs after the main peak (ie, "raise") in the histogram of the first image. Assigned by selecting value). Data pixels in later images considered "calcium oxidized" when the pixel value exceeded this threshold. The percentage of what is considered "oxidized calcium" at any particular time in oven 502 is plotted in Figure 7. The device 200 under test with LLT glass 202 (composition number 1) heat treated at 121 ° C after a 24-hour film attachment step was clearly the most impervious to water and oxygen. As you can see, this experiment was a physically attached T_GIt has been demonstrated that a gentle "anneal" of the low glass thin film layer 202 can restore a substantially poreless barrier layer.

Next, it will be described how the water permeation rate of the device 200 under test was estimated using Table 3 and FIG. The moisture permeation rate of the device 200 under test was estimated by first calculating the total amount of calcium metal in layer 204 at 100 nm. Then, with reference to Figure 7 and other additional data, the time it took for half of the calcium in the 1/2 inch x 1 inch x 100 nm patch to oxidize (the so-called half-life) was estimated. This allows 1 day and 1m in an 85/85 environment²The average number of grams oxidized by the water vapor per hit is obtained. A scale factor was introduced between the ambient time (ambient half-life) and the time spent in the 85/85 environment (85/85 half-life) to convert to ambient conditions. To determine this scale factor, a calcium patch made entirely of calcium and aluminum layers was used, half in an 85/85 oven 502 and the other half left in the atmosphere. The permeation rate measured by the time it took half of the calcium patch placed in the oven to oxidize (1.2 hours) and the time it took half of the calcium patch left in the air to oxidize (163 hours). We were able to estimate the scale factor required to convert to ambient conditions. These values are shown in the underlined part of Table 3.<tables num="3"><img file="JP5113054B2_D0004.tif" /></tables>

The above values are shown graphically as shown in Figures 9A and 9B and can be compared to conventional seals such as the Vitex system Barix seal. Data related to the device 200 under test with LLT glass 204 (composition number 1) heat treated after the adhesion step are shown in Figures 9A and 9B. It also presents data related to the Vitex system's Barix seal. As can be seen, the performance of the device 200 under test was superior to that of devices using the Barix seal. It should be noted that the photographs / graphs in Figure 9B also show the relative levels of oxygen permeability of common polymers and coatings as well as the detection limits of current test equipment.

From the above, it can be easily understood by those skilled in the art that the present invention utilizes an LLT material having a low liquidus temperature to form a barrier layer having the same permeability as the material itself. LLT materials include, but are not limited to, tin fluorophosphate glass, chalcogenide glass, tellurite glass, phosphate glass and borate glass. These LLT materials are particularly suitable for controlling the oxygen and / and moisture degradation commonly found in electronic devices, foods or chemicals. In addition, these LLT materials can be used, for example, to reduce photochemical, hydrolysis, and oxidative damage caused by chemically active penetrants. The LLT material can be adhered using one or more of the methods (eg) such as sputtering, evaporation, spraying, pouring, frit welding, vapor deposition, dip coating, coating or roll coating, spin coating and the like. Defects in the LLT material caused by the adhesion step are removed by the solidification step (heat treatment) in order to form a protective coating on the device that is non-perforated and impervious to gas or moisture. The barrier layer is fairly durable, with low weight loss (0.28%) in a 1000 hour standardized water immersion test at 85 ° C and withstands 600 hours in a calcium patch test in a room at 85 ° C and 85% relative humidity. .. Many attachment methods are possible for ordinary glass (ie, high melting temperature), but the solidification step is really useful because the solidification temperature is sufficient to prevent thermal damage to nearby layers. This is the case for low LLT materials.

In recent experiments performed, for certain LLT materials 202 (ie tin fluorophosphate materials), after being adhered (sputtered) as a film and after the sputtered film has been heat treated, it is T._gWas shown to be high (and with different stoichiometric compositions). Then T between the starting LLT material and both the sputtered (adhesive) film and the heat treated sputtered film._gAn explanation is given to deal with the theory of why (and stoichiometric composition) are different. Basically, in this experiment, all the tin in the original composition number 1 target glass is divalent (ie, Sn).²⁺) Was found. On the other hand, the sputter-deposited thin film material has 66% Sn.⁴⁺And 34% Sn²⁺It consists of. Here, when this sputtered thin film material is heated in vacuum at 120 ° C. for 1 hour, the oxidized state of tin is 100% tetravalent tin (that is, Sn).⁴⁺). These differences in Sn change the stoichiometric composition, resulting in the T of the adherent and heat treated film of composition number 1._gIs also expected to change.

These changes in LT appear to occur with tin fluorophosphate materials, but with the same T as the starting point._gIt should be understood that this does not seem to occur in the case of territe and borate membranes with. In addition, tin pyrophosphate glass (Sn)₂P₂O₇), And T between the sputtered (adhesive) film and the heat-treated sputtered film_gWas investigated to see if it changed. In this test, tin pyrophosphate powder was placed in an evaporative heating boat in a vacuum chamber and pumped 10^-6It was lowered to the vacuum of the tor. The boat was then heated to approximately 80 watts before starting to evaporate the material and attach it to the substrate. The adhering material was then heated in vacuum at 120 ° C. for 1 hour. Subsequent airtightness experiments were performed on the resulting membrane and it was found that the stoichiometric composition of the material was maintained throughout the process. This includes both adherent and heated adherent films.

As used herein, a barrier layer containing a subset of durable low liquidus temperature materials outperforms traditional oxide barrier layers that are physically attached to oxygen and moisture attack (and transport). It has also been shown to provide substantial protection from. For example, the preferred barrier layer described herein has 10 permeation of water and oxygen, respectively.^-6g / m²/ Day and 10^-5cc / m²Can be less than / atm / day. Furthermore, it has been shown that the physically attached low liquidus temperature thin film barrier layer can be annealed at a temperature suitable to keep the physicochemical properties of the adjacent organic layer material intact. I came. This last feature makes the durable low liquidus temperature material unique compared to other physically attached oxide barrier layers. These low liquidus temperature materials can be annealed at low temperatures to remove mesoscopic defects from the physically attached layer and can also retain the physicochemical properties of the adjacent underlying organic layer. This is in contrast to the Vitex method, which does not remove defects. In addition, these low liquidus temperature barrier layers suppress the transport of substances harmful to high performance operation and are used in a variety of devices (eg, waveguides, grating sensors, photonic crystals, etc.). It has been shown that it can be used to form an integral part of.

Although specific types of tin fluorophosphate glass, borate glass and tellurite glass have been described in detail herein, it should be understood that other types of LLT materials can also be used in accordance with the present invention. .. It should also be understood that low liquidus temperature materials can be made that contain small composite materials or other electro-optic dopants. These dopants can optimize the refractive index or impart additional electro-optical features to the device 200. This can be especially useful if the device 200 is a waveguide sensor.

Although some embodiments of the present invention have been described with reference to the accompanying drawings and described in the above-mentioned "best embodiment for carrying out the invention", the present invention is not limited to the disclosed embodiments. It should be understood that a great many reconstructions, modifications and replacements are possible without departing from the gist of the present invention, as shown and described in the scope of the attached patent claims.

<figref num="1">It is a flowchart which illustrates the step of the method of suppressing the deterioration of oxygen and moisture of a device according to this invention.</figref><figref num="2">It is a side sectional view of the device protected by the LLT material applied by the method shown in FIG. 1 according to the present invention.</figref><figref num="3">It is a graph used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="4">It is a graph used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="5">FIG. 5 is a side sectional view used to illustrate various experiments performed to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="6">It is a photograph used to explain various experiments carried out to demonstrate the performance and advantages of the present invention and the results of various experiments.</figref><figref num="7">It is a graph used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="8">It is a perspective view used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="9A">It is a graph used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref><figref num="9B">It is a graph used to explain the various experiments carried out to demonstrate the performance and advantages of the present invention and the results of the various experiments.</figref>